The present invention relates broadly to an IC package test fixture, and more particularly to an in-circuit test apparatus for leaded packages with close lead spacing.
The state of the art of an in-circuit test apparatus for leaded packages with close lead spacing is well represented and alleviated to some degree by the prior art apparatus and approaches which are contained in the following U.S. Pat. Nos.:
U.S. Pat. No. 4,344,033 issued to Stowers et. al. on Aug. 10, 1982;
U.S. Pat. No. 4,667,154 issued to Allerton et. al. on May 19, 1987;
U.S. Pat. No. 4,689,556 issued to Cedrone of Aug. 25, 1987;
U.S. Pat. No. 4,697,143 issued to Lockwood et. al. on Sep. 28, 1987; and
U.S. Pat. No. 4,701,703 issued to Malloy on Oct. 29, 1987.
The Stowers et. al. patent discloses a vacuum actuated test fixture for printed circuit boards which utilizes a yielding diaphragm assembly with rigid frame and spring-loaded diaphragm base plate, to distribute downward atmospheric pressure evenly over the entire area of the board without localized stress concentrations. A captive removable diaphragm frame and quick-acting spring-loaded cam latches assure a positive seal around the margin of the diaphragm assembly and along top and bottom edge portions thereof.
The Allerton et. al. patent describes an electrical contact assembly for a tester which comprises a ring element, a plurality of spring loaded contact probes, an elastic retaining band and alignment pins.
The Cedrone patent discusses a contractor assembly for testing electronic devices that are packaged with a dual-in-line pin array that has an insulating base that mounts two rows of contacts, each adapted to flex into electrical connection with a pin of the device, and a pair of flexible ground planes each spaced closely from an associated one row of said contacts.
The Lockwood et. al. patent is directed to a wafer probe which is provided having metallic transmission lines mounted on a tapered alumina substrate generally surrounded by microwave absorbing material. The probe provides for on-wafer measurements of small planar devices at frequencies from DC to at least 18 GHz with low inductance, and with constant characteristic impedance from the probe external cable terminal to the point of contact on device being probed.
The Malloy patent describes an in-circuit test fixture for use in making a non-functional electrical inspection of individual components and/or circuit paths on a printed circuit board or wired backpanel assembly.
In the prior art, dual-in-line packages which have a 0.1 inch lead spacing, can be probed by hand but with great care. However, as package lead spacing has decreased to the 0.020 inch range, hand probing is no longer practical. Engineers and technicians can no longer hand probe a PC board without serious risk of electrically damaging the outputs (by touching two or more of the outputs simultaneously) or physically damaging the small leads. High density circuit boards utilizing devices with close lead spacing must be designed so that a minimum amount of hand probing is required. However, regardless of the amount of care given to testability features, eventually some problems require hand probing. Hence, some type of test adapter or fixture is needed for high density packages that will gently and precisely attach test connections without requiring elaborate attachment mechanisms.